California Gov. Gavin Newsom visited the U.S.-Mexico border on Monday — but not for the reason you’d expect. The border crisis that drew the Democrat wasn’t immigration, but sewage. For nearly a century, billions of gallons of sewage have been pouring into Southern California from Mexico, making coastal communities near San Diego the victim of a crisis few people know about. The problems have disrupted daily life around America’s eighth-largest city, affected military operations and exposed how generations of politicians in Mexico and the U.S. have failed to provide sanitation on both sides of the world’s busiest border.